400 

 hence when Lv = 0, simplj : 



so that then r becomes a //?i(?^/r function of .r, viz. z'r= i?/ -[-^(Vj* — v/). 

 In the supposed case also tlie following eqnation may be written 

 (see § 2): 



a a ttj a, 



hence also 



i.e. the critical temperature of the "ideal" mixtnre is also a linear 

 function of x, viz. Tk=^ Tu^ -{- x (Tjc^—Tj,^). 

 For «/„s liolds: 



a _ a _ {n^ [/a^ + w, t/aj" _ a^ a, 



when |/aj/t?/ is =z]/ajv^'' in conseqnence of the equality of the 

 critical pressures. In ideal mixtures the critical pressure remains, 

 therefore, constant == ;?a, = pk^^y whatever is the value of x. 



6. Associated components. 



For the calculation of w we can adopt the whole derivation of 

 ^ 2 unchanged; it should only be borne in tnind that, the degree 

 of dissociation of the double molecules of the components being ^^ 

 and /?, in the mixture, that of the /;z<7'<; components will be diflferent, 

 viz. |i/ and |?/. Thence 



(wi e\ + n, e',) — (n, e\ -\- n, e',)„ 

 will not be = now. For we can write e.g. 



«; = ^^{e^)d -f ?, {e^)e ^ {e^)%d + ^, \{e\)e-{e^)Hd\ = (^/kc^ + /?:?„ 



when [e\)d is the energy constant of a double molecule and {e',)e of 

 a single molecule. A similar expression applies to e\. Here e\ and 

 e\ always refer, therefore, to single molecular quantities. The quan- 

 tities 5', and q, are the "pure" heats of dissociation, i.e. without 

 the parts referring to the volume contraction (see further below). 

 For the above expression the following equation may, therefore, be 

 written : 



Further it should be borne in mind that a remains unchanged 

 on dissociation, for on simple joining of two single molecules to 

 one double molecule, I a will likewise become twice as great; 



